Pelletization of pyrolyzed rubber products

ABSTRACT

A system and method for preparing a pelletized carbon black product is provided. The system includes a source of a carbon black product from a pyrolysis process. A mixer is in communication with the source of the carbon black product. A binder oil storage tank is in fluid communication with the mixer. The binder oil storage tank is configured to inject a desired amount of a binder oil into the mixer to form the pelletized carbon black product.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/622,661, filed on Sep. 19, 2012, now issued as U.S. Pat. No.9,139,738, which in turn is a continuation of U.S. patent applicationSer. No. 12/121,339, filed on May 15, 2008, now issued as U.S. Pat. No.8,232,793 which in turn claims priority to U.S. Provisional PatentApplication No. 60/938,480, filed May 17, 2007. The entire disclosuresof the above applications are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to waste recycling and, moreparticularly, to processes for pelletizing carbon black productsproduced by pyrolysis of waste materials.

BACKGROUND OF THE INVENTION

The U.S. Environmental Protection Agency (EPA) estimates thatapproximately 250 million scrap tires are generated in the United Stateseach year. In the United States alone, the Rubber ManufacturersAssociation (RMA) has estimated that between two and three billion scraptires currently reside in landfills or are otherwise stockpiled. Wastetires take up a significant amount of space in landfills, and burying ofthe tires can lead to landfill contamination. Stockpiling waste tiresprovides breeding grounds for pests and represents a significant firehazard. Burning of tires causes a significant amount of air pollution,and run-off from tire fires can contaminate ground water. The handlingand disposal of waste tires is a significant environmental problem, andthe desirability of recycling waste is evident.

One method of recycling waste tires is pyrolysis. Known tire pyrolysisprocesses include heating tires to produce useful products such as oils,gases, recyclable metals, and carbonaceous char. As disclosed in U.S.Pat. Nos. 5,783,046, 6,372,948, and 7,037,410 to Flanigan, the entiredisclosures of which are hereby incorporated herein by reference, aknown pyrolysis process includes heating rubber in the substantialabsence of oxygen to a temperature sufficient to pyrolyze the rubber,distilling a vapor comprising hydrocarbon from the rubber, and producinga solid carbonaceous char. Weinecke et al. in U.S. Pat. No. 7,101,463,hereby incorporated herein by reference in its entirety, describes asystem and process for the recovery of oil from shredded vehicle tiresthat utilizes a pair of sequentially positioned packed towers. Alsodisclosed in U.S. Pat. No. 5,894,012 to Denison, hereby incorporatedherein by reference in its entirety, is a waste processing system thatproduces clear and colorless oil for use in rubber and plasticapplications and a carbonaceous char equivalent to a low structurefurnace black.

The carbonaceous char produced from typical pyrolysis processes isgenerally a friable material. The carbonaceous char can be reduced tofinely-divided particles or “fluff” form through known pulverizationtechniques. However, a mixing and dispersion of finely-divided particlesof carbonaceous char into rubber and plastics is known to beproblematic.

A variety of methods for converting individual particles of carbon blackinto pellets for improved mixing and dispersion are known to the art.For example, a finely-divided carbon black may be agitated under dryconditions in such a manner as to reduce the quantity of air or othergases associated with the carbon black and cause a degree ofagglomeration of the discrete particles of the carbon black. Under wetconditions, the finely-divided carbon black may be agitated in a wetpelletizer in the presence of sufficient liquid pelletizing medium, suchas water or a dilute aqueous solution of a binder such as sugar,molasses, dextrin, starch, calcium lignin sulfonate, and the like, topermit agglomeration of the individual particles into free-flowingpellets of suitable structural strength and stability. However, theapplication of standard carbon black dry and wet pelletizationtechniques to carbonaceous char from pyrolysis processes has notprovided a desirable pelletization quality.

There is a continuing need for a system and method of converting acarbonaceous char from a pyrolysis process to a free-flowing pelletizedform in order to permit inexpensive and convenient handling, storing andshipping thereof. Desirably, a carbon black product produced from thecarbonaceous char is provided in a form convenient for use bymanufacturers of rubber, plastics, and other commercial products.

SUMMARY OF THE INVENTION

In concordance with the instant disclosure, a system and method ofconverting a carbonaceous char from a pyrolysis process to afree-flowing pelletized form in order to permit inexpensive andconvenient handling, storing and shipping thereof, and a carbon blackproduct produced from the carbonaceous char in a form convenient for useby manufacturers of rubber, plastics, and other commercial products, issurprisingly discovered.

In one embodiment, a system for preparing a pelletized carbon blackproduct includes a mixer in communication with a source of carbon blackproduct, such as a carbonaceous char. The mixer is configured to receivethe carbon black product. The system also includes a binder oil storagetank in fluid communication with the mixer. The binder oil storage tankis configured to inject a desired amount of a binder oil into the mixerwith the carbon black product to pelletize the carbon black product.

In a further embodiment, a method for preparing a pelletized carbonblack product comprises the steps of: providing a carbon black product;supplying the carbon black product to a mixer; injecting a binder oilinto the mixer in a desired amount; and mixing the carbon black productand the binder oil, wherein the pelletized carbon black product isformed.

In another embodiment, a pelletized carbon black product includes acarbon black product in an amount greater than about 85 percent byweight relative to the total weight of the pelletized carbon blackproduct. The carbon black product includes a carbon black in an amountbetween about 65 percent and about 98 percent, an organic volatilematerial in an amount between about 1 percent and about 20 percent, andan inorganic ash in an amount in an amount up to about 15 percent. Allpercentages are by weight relative to the total weight of the carbonblack product. The pelletized carbon black product further includes abinder oil in an amount sufficient to agglomerate the carbon blackproduct into substantially free-flowing pellets.

DRAWINGS

The above, as well as other advantages of the present disclosure, willbecome readily apparent to those skilled in the art from the followingdetailed description, particularly when considered in the light of thedrawing described hereafter.

The drawing is a process flow diagram depicting a system for pelletizinga carbonaceous char from a pyrolysis process.

DETAILED DESCRIPTION OF THE INVENTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould also be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features. Inrespect of the methods disclosed, the order of the steps presented isexemplary in nature, and thus, is not necessary or critical.

The present disclosure includes a system 2 and method for pelletizing acarbon black product 4 formed from a carbonaceous char produced bypyrolysis of whole tires, tire shreds, waste feedstocks, waste plasticfeedstocks, medical waste, and the like. An exemplary pyrolysis processis disclosed in Assignee's copending U.S. application Ser. No.12/121,139, filed May 15, 2008, hereby incorporated herein by referencein its entirety. A skilled artisan should understand, however, that thepresent system 2 and method may be employed with the carbon blackproduct 4 produced by another pyrolysis system and process, as desired.

As shown in FIG. 1, the system 2 includes a source 6 of the carbon blackproduct 4. The source 6 may be a post-pyrolysis processing systemconfigured to separate a quantity of extraneous materials, such asfiberglass and metals, from the carbon black product 4 followingpyrolysis of the waste, for example. A mixer 8 is in communication withthe source 6 of carbon black product 4. The mixer 8 is configured toselectively receive the carbon black product 4 from the source 6, asdesired.

The system 2 further includes a binder oil storage tank 10 in fluidcommunication with the mixer 8. The binder oil storage tank 10 isconfigured to selectively inject a desired amount of a binder oil 12into the mixer 8 when the carbon black product 4 is disposed therein.The binder oil tank 10 may have at least one heater 13 coupled theretofor heating the binder oil 12 to a desired temperature. It should beunderstood that the agitation and mixing of the carbon black product 4and the binder oil 12 by the mixer 8 is sufficient to form a pelletizedcarbon black product 14 according to the present disclosure.

In certain embodiments, the mixer 8 is one of a batch drum mixer and arollo-mixer, for example. It should be understood that more than onemixer 8 may be employed in the system 2. The mixer 8 generally isemployed to admix the carbon black product 4 and the binder oil 12 andcause the carbon black product 4 to agglomerate into the pelletizedcarbon black product 14. The mixer 8 may rotate at a rate of up to about500 RPM, for example. In another example, the mixer 8 is heated to atemperature from about 40° F. to about 200° F. to facilitate theadmixing of the carbon black product 4 with the binder oil 12. A skilledartisan should appreciate that other suitable mixers and mixerparameters may be employed as desired.

In particular embodiments, the system 2 further includes a pulverizer16. The pulverizer 16 is configured to reduce the carbon black product 4to a desired particle size. For example, the pulverizer 16 may reducethe carbon black product 4 to about 325 mesh particles. The averageparticle size of the carbon black product 4 may be about five microns,although it should be appreciated that a range of particle sizes may beproduced as desired. In particular, favorable results have been obtainedwhen up to 99.99% of the pulverized carbon black product 4 passesthrough a 325 mesh screen. As a nonlimiting example, the pulverizer 16is a roller mill pulverizer. Other suitable pulverizers 16 may also beemployed.

The pulverizer 16 is disposed between the source 6 of the carbon blackproduct 4 and the mixer 8. The pulverizer 16 is configured to pulverizethe carbon black product 4, generally provided as large friable portionsfrom the pyrolysis process, to the desired particle size. The pulverizer16 may have a pulverizer feed bin 17, for example, which is adapted toselectivity feed the carbon black product 4 to the pulverizer 16. Thecarbon black product 4 may be gravity fed to the pulverizer 16 from thepulverizer feed bin 17. In other embodiments, the carbon black product 4is fed to the pulverizer 16 by a mechanized means, such as a movingbelt, screw, or the like.

The pulverizer 16 is further in communication with the mixer 8 andconfigured to provide the pulverized carbon black product 4 to the mixer8 as desired. The carbon black product 4, when pulverized, may bepneumatically transferable by air conveyance, for example, inconjunction with an air compression system (not shown). A skilledartisan should understand that other means for transferring the carbonblack product 4 through the system 2 may also be employed.

In a further embodiment, the system 2 includes a classifier 18. Theclassifier 18 is configured to selectively provide the carbon blackproduct 4 of the desired particle size to the mixer 8, as desired. Theclassifier 18 is disposed between the pulverizer 16 and the mixer 8. Theclassifier 18 may be employed to separate extraneous material, such asfiberglass, from the carbon black product 4. The classifier 18 may be anair classification unit, for example. A commercially available airclassification unit designed for operation at rotor speeds from about400 RPM to about 2,000 RPM is the Micro-Sizer™ air classificationsystem, manufactured by Progressive Industries, Inc. of Sylacauga, Ala.One of ordinary skill should appreciate that other classifiers 18 mayalso be used.

It should be appreciated that the carbon black product 4, followingpulverization, may be collected and stored in a collection unit 19 forbatch production of the pelletized carbon black product 14. As anonlimiting example, the collection unit 19 may be a product collectioncyclone or centrifugal collector as is known in the art. The productcollection cyclone may use cyclonic action to separate the carbon blackproduct 4 from an air carrier stream, for example. The centrifugal forcecreated by cyclonic action throws the carbon black product 4 toward thewall of the product collection cyclone. After striking the wall, carbonblack product 4 falls into a hopper located underneath the area ofcyclonic action. It should be further understood that other suitablecollection units 19 may also be employed.

The system 2 according to the present disclosure may further include amagnetic separator 20 configured to separate extraneous ferrous materialfrom the carbon black product 4. As a nonlimiting example, thepulverized carbon black product 4 may be metered over the magneticseparator 20 to remove recyclable metal, such as steel belt wire fromtires employed in the pyrolysis process, prior to the pelletization ofthe carbon black product 4. In particular embodiments, the magneticseparator 20 is a rotating magnetic drum. The magnetic separator 20 isdisposed between the source 6 of carbon black product 4 and the mixer 8.The magnetic separator 20 may provide a substantially metal-free carbonblack product 4 for delivery to the mixer 8.

The system 2 may further include a pellet bagger 22 as is known in theart. The pellet bagger 22 is in communication with the mixer 8. Thepellet bagger 22 is configured to bag the pelletized carbon blackproduct 14 produced by the mixer 8 for at least one of handling, storingand shipping. As a nonlimiting example, the pellet bagger 22 isconfigured to fill a supersack with the pelletized carbon black product14. The pellet bagger 22 is in communication with a discharge conveyor24 that delivers the bagged pelletized carbon black 14 to a storagesystem 26 for storing the pelletized carbon black 14 prior to an enduse. Other suitable containers for handling, storing, and shipping thepelletized carbon black product 14 may also be filled. In onealternative embodiment, the system 2 may be adapted to feed thepelletized carbon black 14 directly to a rail car or container, forexample, as desired.

The present disclosure further includes a method for preparing thepelletized carbon black product 14. The method includes the steps ofproviding the carbon black product 4 and supplying the carbon blackproduct 4 to the mixer 8. The binder oil 12 is injected into the mixer 8in a desired amount. The carbon black product 4 and the binder oil 12are admixed to thereby form the pelletized carbon black product 14.

As described hereinabove, the carbon black product 4 is typically acarbonaceous char produced during pyrolysis of a waste material, such aswaste tires. In a particular embodiment, the carbon black product 4 isprovided by a pyrolysis process as disclosed in Assignee's copendingU.S. application Ser. No. 12/121,139. For example, the pyrolysis processincludes the step of depositing a quantity of waste into a porouscontainer, the porous container adapted to allow at least one convectivestream of substantially anaerobic gas to flow therethrough. The porouscontainer is inserted into a pyrolysis thermal processor. The thermalprocessor is sealed and at least one convective stream is circulatedtherethrough. The waste is heated with the convective stream of gasaccording to a time-temperature profile to pyrolyze the waste andproduce the carbon black product 4. The convective stream of gas is thencirculated through a cooler to cool the carbon black product 4. Thecarbon black product 4 is subsequently collected for pelletization inthe mixer 8.

The method further includes the step of pulverizing the carbon blackproduct 4 to a desired particle size prior to supplying the carbon blackproduct 4 to the mixer 8. As described hereinabove, a quantity ofextraneous material may also be separated from the carbon black product4 with at least one of the classifier 18 and the magnetic separator 20prior to supplying the carbon black product 4 to the mixer 8. In aparticular embodiment, the separation includes magnetically separatingthe quantity of ferrous material from the carbon black product 4 toprovide the substantially metal-free carbon black product 4.

The admixing of the carbon black product 4 and the binder oil 12according to the method of the present disclosure produces thepelletized carbon black product 14. It should be appreciated that thecarbon black of the carbon black product 4 includes a substantiallyamorphous carbon. The carbon black product 4 may include carbon black inan amount between about 65 percent and about 98 percent. The carbonblack product 4 further includes an organic volatile material in anamount between about 1 percent and about 20 percent. The carbon blackproduct 4 also includes an inorganic ash in an amount up to about 15percent. All percentages are by weight relative to the total weight ofthe carbon black product 4. The inorganic ash may include elemental zincfrom zinc oxides originally used in the waste rubber as an activator,and inorganic fillers employed in the waste rubber, such as silica andclays, for example. In certain embodiments, the inorganic ash mayinclude a quantity of elemental sulfur, for example, that was employedto originally vulcanize waste rubber.

As a further nonlimiting example, the carbon black product 4 may includebetween about 85 percent and about 95 percent carbon black and about 1percent to about 15 percent residual volatiles in the form of residualpolymer and hydrocarbons remaining at the end of the pyrolysis process.The carbon black product 4 also may include an inorganic ash in anamount up to about 9 percent to about 12 percent. It is surprisinglyfound that the residual volatiles advantageously minimize dusting of thepelletized carbon black product 14 and facilitate dispersion andmiscibility of the pelletized carbon black product 14 in elastomer andoil applications.

The pelletized carbon black product 14 has the binder oil 12 in anamount sufficient to provide a pelletized carbon black product 14 with apellet hardness and fines content suitable for use in rubber mixing, forexample. Pellets must have a sufficient strength to resist physicalbreak down during transportation, but also facilitate dispersion inrubber and plastic compounds. Fines are considered an indicator of bulkhandling and rubber and plastic mixing difficulties. The pelletizedcarbon black product 14 may have a pellet hardness of up to about 40 gf,as a nonlimiting example. As the binder employed to pelletize the carbonblack product 4 an oil, it should be appreciated that the pelletizedcarbon black product 14 is substantially non-dusting and may haveminimal fines content. The amount of the binder oil 12 may be selectedto provide a desirable fines content and level of non-dusting asdesired.

As a nonlimiting example, the binder oil 12 may be used in an amount upto about 15 percent by weight relative to the total weight of thepelletized carbon black product 14. In particular embodiments, thebinder oil 12 in an amount of about 12.5 percent by weight relative tothe total weight of the pelletized carbon black product 14 is sufficientto form pellets with the desired characteristics. As nonlimitingexamples, the binder oil 12 is at least one of a highly aromatic oil, anaphthenic oil, and a paraffinic oil. It should be appreciated thatproduct oil derived from the pyrolysis process may also be used as abinder oil 12. A skilled artisan may select other suitable binder oils12 and levels as desired.

Individual pellets of the pelletized carbon black product may have anaverage diameter from about 0.125 inches to about 0.0625 inches, forexample. In other embodiments, the pellets produced according to thepresent method may fall within a desired range of about 18 to about 60mesh, for example. The individual pellets of the pelletized carbon blackproduct 14 may be substantially spherical, although one of ordinaryskill in the art should understand that the pelletized carbon blackproduct 14 may be provided other shapes that facilitate flowability ofthe pelletized carbon black product 14. The pelletization processminimizes product dusting, and improves density and flow propertiesassociated with the carbon black product 4 produced by pyrolysis ofwaste. The pelletized carbon black product 14 may then be stored, forexample, in a silo, supersack or in small bags for delivery and thedesired end use.

It should be appreciated that the pelletized carbon black product 14according to the present disclosure provides for an optimized dispersionand miscibility of the carbon black product 4 in rubber and plasticcompounds, particularly in comparison to known pyrolysis productsprovided in fluff form. It is surprisingly found that the use of thebinder oil 12, in conjunction with the residual volatiles of thepelletized carbon black product 4, advantageously minimizes dusting ofthe pelletized carbon black product 14.

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes may be made without departingfrom the scope of the disclosure, which is further described in thefollowing appended claims.

What is claimed is:
 1. A method for preparing a pelletized carbon blackproduct, comprising the steps of: providing a carbon black product,wherein the carbon black product is a carbonaceous char produced bypyrolysis of waste, the pyrolysis performed by depositing a quantity ofthe waste into a porous container, the porous container adapted to allowat least one convective stream of substantially anaerobic gas to flowtherethrough, inserting the porous container into a pyrolysis thermalprocessor, sealing the thermal processor, circulating the at least oneconvective stream of gas in the pyrolysis thermal processor, heating thewaste with the convective stream of gas according to a time-temperatureprofile to form the carbon black product, cooling the carbon blackproduct by circulating the at least one convective stream of gas througha cooler, and collecting the carbon black product; pulverizing thecarbon black product to a predetermined particle size using apulverizer; classifying the pulverized carbon black product using aclassifier; magnetically separating a quantity of ferrous material fromthe pulverized and classified carbon black product to make the carbonblack product substantially metal-free; supplying the pulverized,classified, and substantially metal free carbon black product to apelletization subsystem; and pelletizing the pulverized, classified, andsubstantially metal free carbon black product using the pelletizationsubsystem, wherein the step of pelletizing the pulverized, classified,and substantially metal free carbon black product using thepelletization subsystem further includes the steps of injecting a liquidpelletizing medium into a mixer in a predetermined amount, and mixingthe carbon black product and the liquid pelletizing medium in the mixer,wherein the pelletized carbon black product is formed, and wherein themixer is configured to be heated to a temperature from about 40 degreesF. to about 200 degrees F. to facilitate the admixing of pulverized andsubstantially metal free carbon black product with the liquidpelletizing medium.
 2. The method according to claim 1, wherein theliquid pelletizing medium is a binder oil.
 3. The method according toclaim 1, further comprising the step of bagging the pelletized carbonblack product for at least one of handling, storing, and shipping. 4.The method according to claim 1, wherein the step of pulverizing thecarbon black product reduces the carbon black product to about 325 meshparticles.
 5. The method according to claim 4, wherein up to 99.99% ofthe pulverized carbon black product passes through a 325 mesh screen. 6.The method according to claim 1, wherein the step of pelletizing thepulverized, classified, and substantially metal free carbon blackproduct using the pelletization subsystem results in a pelletized carbonblack product having an average diameter from about 0.125 inches toabout 0.0625 inches.